Bonding to Teeth
No description yet. This curated deck is ready for daily study.
Card preview (13)
what are the ideal properties of a dental adhesive?
• provide a high bond strength to tooth tissues • immediate high strength bond • durable bond • impermeable bond • easy to use • safe
what does the etching of enamel provide?
• increased surface energy of the enamel • therefor better wettability • allows resin to adapt better to roughened surface
what acid is most commonly used to etch enamel?
30% phosphoric acid
why is bonding to dentine more complicated that bonding to enamel?
• dentine is WET (due to permeable tubules) • dentine has a low surface energy • dentine is hydrophilic whereas most bonding agents are hydrophobic
what are the requirements of a dentine bonding agent?
• ability to flow • potential for intimate contact with dentine surface • low viscosity • adhesion to substrate
what is the effect of bonding agents to the surface of dentine?
dentine bonding agents INCREASE THE SURFACE AREA of dentine & allow composite to flow and stick to it
what is the smear layer?
the smear layer is an adherent layer of organic debris that remains on the dentine surface after the preparation of the dentine during the restoration of a tooth
what effect does etching have on the smear layer?
remove and/or modify the smear layer from dentine
what is the function of phosphoric acid applied to dentine as a conditioner?
• removes smear layer • opens dentinal tubules by removing smear plugs • decalcifies the uppermost layer of the dentine
in terms of bonding to dentine, what is the primer and how does it function?
• the primer is really the adhesive element • its a coupling agent • it contains a bifunctional molecule with a hydrophilic end to bond to dentine and a hydrophilic end to bond to resin
what is a common coupling agent found in bonding primers? how does it work?
HEMA - contains a C=C bone which opens and forms a strong covalent bone with the next resin layer
in dentine bonding agents, how does the adhesive work?
• predominately hydrophobic • penetrates the primed dentine which now has a hydrophobic surface • forms a micromechanical bond within the tubules and exposed dentinal collagen fibres • formed the HYBRID LAYER of collagen plus resin
what can happen if the dentine is over etched?
• collapse of the collagen fibres so no resin can penetrate - too deep an etch and primer cannot penetrate full depth